Assessment of trabecular meshwork width using swept source optical coherence tomography

Purpose: Measurements of the angle width by ultrasound biomicroscopy or anterior segment optical coherence tomography are usually performed 500 μm from the scleral spur, as the anterior part of trabecular meshwork (TM) is assumed to lie within this distance. The aim of this study was to measure TM width using swept source optical coherence tomography (SS-OCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan), and to investigate factors influencing this measurement. Methods: Participants underwent gonioscopy and SS-OCT imaging in the dark. High-definition SS-OCT images were corrected for refractive distortion; and customized software (ImageJ; National Institutes of Health, Bethesda, MD, USA) was utilized to measure TM width (distance between the scleral spur and Schwalbe's line). Linear regression analysis was performed to assess the relationship between TM width with demographic and angle parameters. Results: One hundred and forty eight Chinese subjects were analyzed. The majority was female (62.4 %); the mean age was 59.2 ± 8.68 years. Identification of the scleral spur and Schwalbe's line with SS-OCT was possible in 590 (99.7 %) and 585 angle quadrants (98.8 %) respectively. TM width was wider in the inferior and superior quadrants (mean 889 [SD 138] and 793 [136] μm), compared to the nasal and temporal quadrants (712 [137] and 724 [115] μm, P < 0.001). There was a difference in average TM width between open (789 [100]) and closed angle eyes (753 [86]) (P = 0.048). There was no significant association between TM width and angle parameters, laterality, or demographic factors. Conclusions: In SS-OCT HD images, the mean TM width varied from 710 to 890 μm in the different quadrants of the eye, and the inferior quadrant TM was the widest compared to other quadrants.